Magnetic and MO media are widely employed in various applications, particularly in the computer industry for data/information storage and retrieval purposes. A magnetic medium in e.g., disk form, such as utilized in computer-related applications, comprises a non-magnetic substrate, e.g., of glass, ceramic, glass-ceramic composite, polymer, metal, or metal alloy, typically an aluminum (Al)-based alloy such as aluminum-magnesium (Al—Mg), having at least one major surface on which a layer stack comprising a plurality of thin film layers constituting the medium are sequentially deposited. Such layers may include, in sequence from the workpiece (substrate) deposition surface, a plating layer, e.g., of amorphous nickel-phosphorus (Ni—P), a polycrystal line underlayer, typically of chromium (Cr) or a Cr-based alloy such as chromium-vanadium (Cr—V), a magnetic layer, e.g., of a cobalt (Co)-based alloy, and a protective overcoat layer, typically of a carbon-based material having good mechanical (i.e., tribological) properties. A similar situation exists with MO media, wherein a layer stack is formed which comprises a reflective layer, typically of a metal or metal alloy, one or more rare-earth thermo-magnetic (RE-TM) alloy layers, one or more dielectric layers, and a protective overcoat layer, for functioning as reflective, transparent, writing, writing assist, and read-out layers, etc.
According to conventional manufacturing methodology, a majority of the above-described layers constituting magnetic and/or MO recording media are deposited by cathode sputtering, typically by means of multi-cathode and/or multi-chamber sputtering apparatus wherein a separate cathode comprising a selected target material is provided for deposition of each component layer of the stack and the sputtering conditions are optimized for the particular component layer to be deposited. Each cathode comprising a selected target material can be positioned within a separate, independent process chamber, in a respective process chamber located within a larger chamber, or in one of a plurality of separate, interconnected process chambers each dedicated for deposition of a particular layer. According to such conventional manufacturing technology, a plurality of media substrates, typically in disk form, are serially transported by means of a multi-apertured pallet or similar type holder, in linear or circular fashion, depending upon the physical configuration of the particular apparatus utilized, from one sputtering target and/or process chamber to another for sputter deposition of a selected layer thereon.
Cost-effective productivity requirements imposed by automated manufacturing technology for magnetic and MO media require maximized sputter deposition rates, while at the same time, high quality, high areal recording density media require high purity thin film layers which exhibit respective physical, chemical, and/or mechanical properties, including, inter alia, proper crystal morphology necessary for obtaining high areal recording densities, e.g., polycrystallinity; good magnetic properties, e.g., coercivity and squareness ratio; chemical stability, e.g., inertness or corrosion resistance; and good tribological properties, e.g., wear resistance and low stiction/friction. Frequently, obtainment of such desirable physical, chemical, and/or mechanical properties for each of the constituent layers of the multi-layer media requires application of an electrical bias potential to the substrate during sputtering, e.g., a DC, AC, or RF bias potential, or some combination thereof, wherein the bias type and level of bias potential is optimized for each constituent layer.
For example, application of a suitable substrate bias during sputter deposition of metal-based underlayers and ferromagnetic metal alloy layers of thin film magnetic recording media can facilitate obtainment of preferred crystal orientations, and increase carbon (C) density of C-based protective overcoat layers of thin film magnetic and MO recording media. Application of suitable substrate bias potentials to metal-based substrates, e.g., Al or Al alloy disks, poses no significant problem in the continuous, automated manufacture of hard disk recording media, inasmuch as the electrically conductive disks are in electrical contact with the metal-based pallet utilized for transporting a plurality of disks in, e.g., vertical orientation, past a series of sputtering sources, which metal-based (e.g., Al-based) pallet can be easily electrically biased via sliding contacts at the base thereof.
However, application of suitable substrate bias to electrically insulative substrates during multi-layer sputter deposition thereon, e.g., as with recording media with glass, ceramic, glass-ceramic, or polymer-based substates, is problematic. According to current manufacturing practice in the manufacture of magnetic and/or MO recording media utilizing biassed sputter deposition onto non-conductive substrates, a problem arises in that the small tabs on the pallet required for holding the substrates (e.g., disks) vertically erect and on edge in the pallet apertures act to shield edge portions of the substrates from metal deposition, leaving the substrates uncoated at the points of contact with the pallet tabs. As a consequence, reliable electrical contact to the substrates for bias potential application during that deposition step and subsequent deposition steps cannot be established, and a metal coating layer must be preliminarily applied to the substrate surface(s) in a separate deposition system which provides full surface coverage. Disadvantageously, however, the current practice with non-conductive substrates, e.g., glass disks, of over-coating the entire surface(s) thereof with a metal layer in a separate vacuum system prior to multi-layer media deposition thereon involves several additional processing steps and expense.
Accordingly, there exists a need for improved means and methodology for vapor depositing, e.g., by sputtering techniques, at deposition rates consistent with the throughput requirements of automated manufacturing processing, multi-layer thin film stacks and laminates on the surfaces of a plurality of substrates carried by a common pallet, which means and methodology overcomes the drawback associated with the difficulty in applying a desired substrate bias during film deposition, as described supra. More specifically, there exists a need for improved means and methodology for sputtering high purity, high quality, thin film layer stacks or laminates having optimal physical, chemical, and/or mechanical properties for use in the manufacture of single- and/or dual-sided magnetic and/or MO media, e.g., in the form of disks, which means and methodology provide rapid simple, and cost-effective formation of such media, as well as various other products and manufactures comprising at least one thin film layer.
In particular, the present invention addresses and solves problems attendant upon sputter deposition of thin film layers onto electrically biased workpieces comprised of electrically insulative substrate materials, which thin film deposition is utilized, inter alia, in the manufacture of high quality, thin film magnetic and/or MO recording media, while maintaining full compatibility with all aspects of conventional automated manufacturing technology therefor. Further, the means and methodology afforded by the present invention enjoy diverse utility in the manufacture of various devices and articles requiring high purity, high quality thin films with optimal physical, chemical, and/or mechanical properties.